Mega irrigation projects along Tana River linked to deadly diseases

Scientists have linked mega irrigation projects to the rise of disease causing mosquitoes along Tana River Basin.

A joint team from the Kenya Medical Research Institute (Kemri), International Livestock Research Institute and the University of Nairobi says projects done without proper impact assessment are exposing locals to serious health risks.

While mega irrigation projects are the government’s major drivers for increased food production, researchers in a new report say not enough investigations are being done to understand their possible negative health effects and how they can be mitigated.

Mosquitoes

The team cites the presence of Hola and Bura irrigation schemes on Tana River as presenting serious environmental concerns. A later addition is the Galana-Kulalu Food Security Project though not part of the study.

“No initial assessment is being conducted to evaluate potential impacts of irrigation on the environment, human and animal health,” says the study.

Specifically, the team investigated how the Bura irrigation scheme, has affected human disease causing mosquitoes along the Tana River Basin.

They collected about 40,000 different types of mosquitoes from 11 irrigated villages during a two-year period from 2013 at the Bura scheme.
“We found an overall increase of disease causing mosquitoes, which was directly linked to the presence of Bura Irrigation Scheme,” says the study.

Of major concern, the team says is the proliferation of mosquitoes which transmit the Rift Valley Fever (RVF) that is endemic in the area. Both Tana River and neighbouring Garissa counties were heavily affected by the two major RVF out breaks of the 1997–1998 and 2006–2007.

The researchers warn that the irrigation scheme has increased the risk of disease outbreaks including the West Nile Viral disease and other emerging illnesses.

Published on December 23 by Oxford University Press in the Journal of Medical Entomology it was led by Dr Rosemary Sang ‎a Chief Research Officer at US Army Medical Research Unit – Kemri.

The Bura Irrigation Scheme comprises 10,000 acres divided into several blocks, each measuring between 216 and 720 acres, and contains 2,200 homesteads in 11 villages.
The researchers used the non irrigated Murukani village, situated 15 km from the scheme as control to compare mosquito densities in the irrigated and non irrigated villages.
The study reports an increase in the number of mosquito species which transmit Rift Valley Fever Virus and the West Nile Virus, in irrigated villages compared to the Murukani site.

“This is because of the availability of many artificial breeding habitats being flooded for longer periods, allowing for proliferation of large mosquito populations that also survive for longer because of high levels of humidity,” says the study.
The authors also found the proliferation of other less known but also dangerous disease causing agents and warn they could trigger new outbreaks. The study also names Semliki Forest Virus, Pongola virus, Babanki virus and Ndumu virus all closely connected to the RFV as possible health risks to the Tana River Basin residents.

— Source: Rocket Science